Buggy code:
public class ThreadGroupGui extends AbstractJMeterGuiComponent implements ItemListener { LoopControlPanel loopPanel ; private VerticalPanel mainPanel ; private static final String THREAD_NAME = "Thread<seq2seq4repair_space>Field" ; private static final String RAMP_NAME = "Ramp<seq2seq4repair_space>Up<seq2seq4repair_space>Field" ; private JTextField threadInput ; private JTextField rampInput ; private static final String SCHEDULER = "scheduler" ; private static final String START_TIME = "start_time" ; private static final String END_TIME = "end_time" ; private JDateField start ; private JDateField end ; private JCheckBox scheduler ; public ThreadGroupGui ( ) { } public Collection getMenuCategories ( ) { } public TestElement createTestElement ( ) { } public void modifyTestElement ( TestElement tg ) { } public void configure ( TestElement tg ) { } public void itemStateChanged ( ItemEvent ie ) { } public JPopupMenu createPopupMenu ( ) { } public JPanel createControllerPanel ( ) { } private JPanel createStartTimePanel ( ) { } private JPanel createEndTimePanel ( ) { } public String getStaticLabel ( ) { } private void init ( ) { setLayout ( new BorderLayout ( 0 , 5 ) ) ; setBorder ( makeBorder ( ) ) ; add ( makeTitlePanel ( ) , BorderLayout . NORTH ) ; VerticalPanel threadPropsPanel = new VerticalPanel ( ) ; threadPropsPanel . setBorder ( BorderFactory . createTitledBorder ( BorderFactory . createEtchedBorder ( ) , JMeterUtils . getResString ( "thread_delay_properties" ) ) ) ; JPanel threadPanel = new JPanel ( new BorderLayout ( 5 , 0 ) ) ; JLabel threadLabel = new JLabel ( JMeterUtils . getResString ( "number_of_threads" ) ) ; threadPanel . add ( threadLabel , BorderLayout . WEST ) ; threadInput = new JTextField ( "1" , 5 ) ; threadInput . setName ( ThreadGroupGui . THREAD_NAME ) ; threadLabel . setLabelFor ( threadInput ) ; threadPanel . add ( threadInput , BorderLayout . CENTER ) ; threadPropsPanel . add ( threadPanel ) ; new FocusRequester ( threadInput ) ; JPanel rampPanel = new JPanel ( new BorderLayout ( 5 , 0 ) ) ; JLabel rampLabel = new JLabel ( JMeterUtils . getResString ( "ramp_up" ) ) ; rampPanel . add ( rampLabel , BorderLayout . WEST ) ; rampInput = new JTextField ( "1" , 5 ) ; rampInput . setName ( ThreadGroupGui . RAMP_NAME ) ; rampLabel . setLabelFor ( rampInput ) ; rampPanel . add ( rampInput , BorderLayout . CENTER ) ; threadPropsPanel . add ( rampPanel ) ; threadPropsPanel . add ( createControllerPanel ( ) ) ; scheduler = new JCheckBox ( JMeterUtils . getResString ( "scheduler" ) ) ; scheduler . addItemListener ( this ) ; threadPropsPanel . add ( scheduler ) ; mainPanel = new VerticalPanel ( ) ; <START_BUG> mainPanel . setBorder ( BorderFactory . createTitledBorder ( BorderFactory . createEtchedBorder ( ) , JMeterUtils . getResString ( "scheduler_cofiguration" ) ) ) ; <END_BUG> mainPanel . add ( createStartTimePanel ( ) ) ; mainPanel . add ( createEndTimePanel ( ) ) ; mainPanel . setVisible ( false ) ; VerticalPanel intgrationPanel = new VerticalPanel ( ) ; intgrationPanel . add ( threadPropsPanel ) ; intgrationPanel . add ( mainPanel ) ; add ( intgrationPanel , BorderLayout . CENTER ) ; } public void setNode ( JMeterTreeNode node ) { } public Dimension getPreferredSize ( ) { } }

Fix:
mainPanel . setBorder ( BorderFactory . createTitledBorder ( BorderFactory . createEtchedBorder ( ) , JMeterUtils . getResString ( "scheduler_configuration" ) ) ) ;